1. Field of the Invention
The present invention relates to equipment for cleaning articles to be cleaned such as electric parts, electronic parts, machine parts, optical related parts, resin processed articles, printing screens or the like, by the use of flammable solvent.
2. Description of the Prior Art
Conventionally, in the case where articles to be cleaned such as electric parts, electronic parts, machine parts, optical related parts, resin processed articles, printing screens or the like are cleaned, it has been common to use halogenated organic compounds such as CFC (Chloro Fluoro Carbon), trichloroethane and the like, which are nonflammable.
It has been found, however, that these inflammable solvents are harmful to the global environment as such represented by depletion of the ozone layer or the like. It is becoming difficult to use such chemicals as cleaning solvents hereafter.
As cleaning chemicals in place of these nonflammable solvents, there exist flammable solvents, for example, alcohols such as methanol, ethanol, isopropyl alcohol and the like, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and the like, or petroleum fractions such as benzene, toluene, xylene, naphtha, kerosene or the like. Although these flammable solvents have a superior cleanability, they are generally volatile and are easily ignitable. Thus, it often leads to a disaster brought by a fire, an explosion and the like, if these flammable solvents are used in the cleaning equipment.
For this reason, in order to conduct the cleaning by the use of the aforesaid flammable solvents, it is necessary to prevent the equipment from attaining a condition in which combustion of these solvents is made possible, by the fact that the communication of gas between the cleaning atmosphere within the cleaning equipment and the outside air is cut off, by the fact that, even if air leaks into the equipment, the air is selectively discharged to the outside of the system, or the like.
However, there are no economical and reliable techniques to prevent from attaining the said condition. Thus, until now, it has been practically difficult to unitize the flammable solvents for cleaning the articles to be cleaned.
Further, in order to remove unnecessary solid materials which are contained in the solvent as the result of the cleaning, it has been common to use a method in which the cleaning solvent recirculated by pump passes through a filter to date. However, the method is complicated mechanically, and it is difficult to remove contaminant components dissolved in the cleaning solvent.
Furthermore, the conventional cleaning equipment has no function to discharge only the contaminant components to the outside of the equipment while the cleaning solvent is kept confined within the equipment, even if a distillation apparatus is provided in which the cleaning solvent contaminated in the course of cleaning is regenerated by distillation. Accordingly, it is required that the equipment is halted and the used solvent is replaced with new solvent eventually.
For the reasons discussed above, the expenses for treating the used solvent and also for purchasing the new solvent are required so that not only the running cost increases, but also there is a possibility that treatment of the used solvent may cause an environmental problem with the conventional equipment.